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Wendelin Werner

Publications and source records attributed to Wendelin Werner.

At least 37 records · Page 2Linked to original sources
arXiv2015

A note on Ising random currents, Ising-FK, loop-soups and the Gaussian free field

We make a few elementary observations that relate directly the items mentioned in the title. In particular, we note that when one superimposes the random current model related to the Ising model with an independent Bernoulli percolation model with well-chosen weights, one obtains exactly the FK-percolation (or random cluster model) associated with the Ising model. We also point out that this relation can be interpreted via loop-soups, combining the description of the sign of a Gaussian Free Field on a discrete graph knowing its square (and the relation of this question with the FK-Ising model) with the loop-soup interpretation of the random current model.

math.PR↗
arXiv2015

A simple renormalization flow for FK-percolation models

We present a setup that enables to define in a concrete way a renormalization flow for the FK-percolation models from statistical physics (that are closely related to Ising and Potts models). In this setting that is applicable in any dimension of space, one can interpret perturbations of the critical (conjectural) scaling limits in terms of stationary distributions for rather simple Markov processes on spaces of abstract discrete weighted graphs.

math.PR↗
arXiv2014

The nested simple conformal loop ensembles in the Riemann sphere

Simple conformal loop ensembles (CLE) are a class of random collection of simple non-intersecting loops that are of particular interest in the study of conformally invariant systems. Among other things related to these CLEs, we prove the invariance in distribution of their nested "full-plane" versions under the inversion $z \mapsto 1/z$.

math.PR↗
arXiv2012

On conformally invariant CLE explorations

We study some conformally invariant dynamic ways to construct the Conformal Loop Ensembles with simple loops introduced in earlier papers by Sheffield, and by Sheffield and Werner. One outcome is a conformally invariant way to measure a distance of a CLE(4) loop to the boundary "within" the CLE(4), when one identifies all points of each loop.

math.PR↗
arXiv2012

From CLE(κ) to SLE(κ,ρ)'s

We show how to connect together the loops of a simple Conformal Loop Ensemble (CLE) in order to construct samples of chordal SLE(κ) processes and their SLE(κ,ρ) variants, and we discuss some consequences of this construction.

math.PR↗
arXiv2012

The Markovian hyperbolic triangulation

We construct and study the unique random tiling of the hyperbolic plane into ideal hyperbolic triangles (with the three corners located on the boundary) that is invariant (in law) with respect to Moebius transformations, and possesses a natural spatial Markov property that can be roughly described as the conditional independence of the two parts of the triangulation on the two sides of the edge of one of its triangles.

math.PR↗
arXiv2011

Conformal Loop Ensembles: Construction via Loop-soups

The two-dimensional Brownian loop-soup is a Poissonian random collection of loops in a planar domain with an intensity parameter c. When c is not greater than 1, we show that the outer boundaries of the loop clusters are disjoint simple loops (when c>1, there is almost surely only one cluster) that satisfy certain conformal restriction axioms. We prove various results about loop-soups, cluster sizes, and the c=1 phase transition. Combining this with the results of another paper of ours on the Markovian characterization of simple conformal loop ensembles (CLE), this proves that these outer boundaries of clusters of Brownian loops are in fact SLE(k) loops for k in (8/3, 4]. More generally, it completes the proof of the fact that the following three descriptions of simple CLEs (proposed in earlier works by the authors) are equivalent: (1) The random loop ensembles traced by branching Schramm-Loewner Evolution (SLE(k)) curves for k in (8/3, 4]. (2) The outer-cluster-boundary ensembles of Brownian loop-soups. (3) The (only) random loop ensembles satisfying the conformal restriction axioms.

math.PR↗
arXiv2011

Conformal Loop Ensembles: The Markovian characterization and the loop-soup construction

For random collections of self-avoiding loops in two-dimensional domains, we define a simple and natural conformal restriction property that is conjecturally satisfied by the scaling limits of interfaces in models from statistical physics. This property is basically the combination of conformal invariance and the locality of the interaction in the model. Unlike the Markov property that Schramm used to characterize SLE curves (which involves conditioning on partially generated interfaces up to arbitrary stopping times), this property only involves conditioning on entire loops and thus appears at first glance to be weaker. Our first main result is that there exists exactly a one-dimensional family of random loop collections with this property---one for each k in (8/3,4]---and that the loops are forms of SLE(k). The proof proceeds in two steps. First, uniqueness is established by showing that every such loop ensemble can be generated by an "exploration" process based on SLE. Second, existence is obtained using the two-dimensional Brownian loop-soup, which is a Poissonian random collection of loops in a planar domain. When the intensity parameter c of the loop-soup is less than 1, we show that the outer boundaries of the loop clusters are disjoint simple loops (when c>1 there is almost surely only one cluster) that satisfy the conformal restriction axioms. We prove various results about loop-soups, cluster sizes, and the c=1 phase transition. Taken together, our results imply that the following families are equivalent: 1. The random loop ensembles traced by certain branching SLE(k) curves for k in (8/3, 4]. 2. The outer-cluster-boundary ensembles of Brownian loop-soups for c in (0, 1]. 3. The (only) random loop ensembles satisfying the conformal restriction axioms.

math.PR↗
arXiv2010

Some locally self-interacting walks on the integers

We study certain self-interacting walks on the set of integers, that choose to jump to the right or to the left randomly but influenced by the number of times they have previously jumped along the edges in the finite neighbourhood of their current position (in the present paper, typically, we will discuss the case where one considers the neighbouring edges and the next-to-neighbouring edges). We survey a variety of possible behaviours, including some where the walk is eventually confined to an interval of large length. We also focus on certain "asymmetric" drifts, where we prove that with positive probability, the walks behave deterministically on large scale and move like a constant times the square root of time, or like a constant times the logarithm of time.

math.PR↗
arXiv2010

Stuck Walks

We investigate the asymptotic behaviour of a class of self-interacting nearest neighbour random walks on the one-dimensional integer lattice which are pushed by a particular linear combination of their own local time on edges in the neighbourhood of their current position. We prove that in a range of the relevant parameter of the model such random walkers can be eventually confined to a finite interval of length depending on the parameter value. The phenomenon arises as a result of competing self-attracting and self-repelling effects where in the named parameter range the former wins.

math.PR↗
arXiv2010

Random soups, carpets and fractal dimensions

We study some properties of a class of random connected planar fractal sets induced by a Poissonian scale-invariant and translation-invariant point process. Using the second-moment method, we show that their Hausdorff dimensions are deterministic and equal to their expectation dimension. We also estimate their low-intensity limiting behavior. This applies in particular to the "conformal loop ensembles" defined via Poissonian clouds of Brownian loops for which the expectation dimension has been computed by Schramm, Sheffield and Wilson.

math.PR↗
arXiv2007

Asymmetry of near-critical percolation interfaces

We study the possible scaling limits of percolation interfaces in two dimensions on the triangular lattice. When one lets the percolation parameter p(N) vary with the size N of the box that one is considering, three possibilities arise in the large-scale limit. It is known that when p(N) does not converge to 1/2 fast enough, then the scaling limits are degenerate, whereas if p(N) - 1 / 2 goes to zero quickly, the scaling limits are SLE(6) as when p=1/2. We study some properties of the (non-void) intermediate regime where the large scale behavior is neither SLE(6) nor degenerate. We prove that in this case, the law of any scaling limit is singular with respect to that of SLE(6), even if it is still supported on the set of curves with Hausdorff dimension equal to 7/4.

math.PR↗
arXiv2006

The conformally invariant measure on self-avoiding loops

We show that there exists a unique (up to multiplication by constants) and natural measure on simple loops in the plane and on each Riemann surface, such that the measure is conformally invariant and also invariant under restriction (i.e. the measure on a Riemann surface S' that is contained in another Riemann surface S, is just the measure on S restricted to those loops that stay in S'). We study some of its properties and consequences concerning outer boundaries of critical percolation clusters and Brownian loops.

math.PR↗
arXiv2005

Some recent aspects of random conformally invariant systems

These are the lecture notes from a course given in July 2005 at the summer school in Les Houches. We describe some recent results concerning two-dimensional conformally invariant systems. In particular, we discuss conformally invariant measures on loops and conformal loop-ensembles (CLE).

math.PR↗
arXiv2003

SLEs as boundaries of clusters of Brownian loops

In this research announcement, we show that SLE curves can in fact be viewed as boundaries of certain simple Poissonian percolation clusters: Recall that the Brownian loop-soup (introduced in the paper arxiv:math.PR/0304419 with Greg Lawler) with intensity c defines a Poissonian collection of (simple if one focuses only on the outer boundary) loops in a domain. This random family of (possibly intersecting) loops is conformally invariant (and there are almost surely infinitely many small loops in any sample). We show that there exists a critical value a in (0,1] such that if one colors all the interiors of the loops, the obtained clusters are bounded when c a, one single cluster fills the domain. We prove that for small c, the outer boundaries of the clusters are SLE-type curves where $κ\le 4$ and $c$ related by the usual relation $c=(3κ-8)(6-κ)/2κ$ (i.e. c corresponds to the central charge of the model). Conjecturally, the critical value a is equal to one and corresponds to SLE4 loops, so that this should give for any c in (0,1] a construction of a natural countable family of random disjoint SLE$_κ$ loops (i.e. $κ$ should span $(8/3,4]$), that behaves ``nicely'' under perturbation of the domain. A precise relation between chordal SLE and the loop-soup goes as follows: Consider the sample of a certain restriction measure (i.e. a certain union of Brownian excursions) in a domain, attach to it all the above-described clusters that it intersects. The outer boundary of the obtained set is exactly an SLE$_κ$, if the restriction measure exponent is equal to the highest-weight of the corresponding representation with central charge c.

math.PR↗
arXiv2003

Conformal restriction and related questions

This paper is based on mini-courses given in July 2003. Its goal is to give a self-contained sketchy and heuristic survey of the recent results concerning conformal restriction, that were initiated in our joint work with Greg Lawler and Oded Schramm, and further investigated in the last year in joint work with Roland Friedrich, Greg Lawler, and by Julien Dubedat. These notes can be viewed as complementary to my Saint-Flour notes.

math.PR↗
arXiv2003

Conformal restriction, highest-weight representations and SLE

We show how to relate Schramm-Loewner Evolutions (SLE) to highest-weight representations of infinite dimensional Lie Algebras using the conformal restriction properties studied by Lawler, Schramm and Werner in the paper arXiv:math.PR/0209343. This confirms the prediction from theoretical physics and conformal field theory that two-dimensional critical systems are related to such degenerate representations.

math-ph↗